Redundancy and functions

AN4124

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Doc ID 023294 Rev 2

A.3.2

Example N2: fake CF by external IRQ

In this example we show the CF fault injection (by external IRQ funtionality), in order to

show an FCCU reaction. The example includes NMI ISR assertion. The fault is checked and

cleared with subroutine by looking in the CFSx registers.

This example employs the CF external button (KEY 1) to inject and clear, and the LED1 on

the motherboard to view the fault. To connect the button to input pins (interrupt), we need to

connect J8 pin 1B to JP9 pin 1.

The flow is:

●

Blink LED1

●

Press KEY1: to inject asynchronous external IRQ (ISR)

●

External IRQ (ISR)

–

Fake CF

–

LED1 off

–

FCCU STATE = FAULT

–

DEVICE STATE = SAFE

–

RESET

–NMI IRQ (ISR)

●

After RESET: unmask NMI

●

NMI IRQ (ISR)

–

Clear FCCU FAULT and return to main